The present invention relates to a new and improved photometric method for the quantitative determination of a substance or material in an analysis substance, wherein the course of the calibration curve representative of the functional dependency of an optical measurement magnitude or value upon the concentration of the substance can be at least approximately determined by at most several of few parameters, and this invention further pertains to a new and improved construction of photoelectric photometer for the performance of the aforesaid method.
With the heretofore known photometric measurement techniques for the determination of the concentration of a substance or material, for instance in a liquid mixture, there is plotted a calibration curve of the relevant mixture by means of standard-calibration solutions. To determine the concentration there is then measured at spaced time intervals the analysis sample as well as the calibration solution and from the measurement results or values there is determined with the aid of the calibration curve the unknown substance concentration. If the substance or material to be analyzed is not light-absorbing or absorbs light only to a slight extent, then such material is reacted with a specific reagent, so that the resultant product possesses light-absorption properties in a predetermined spectral range or fluorescence, and the degree of transmissibility or absorption of the mixture and the intensity of the fluorescence, respectively, constitute optical measurement magnitudes or values for the determination of the concentration. A prerequisite for the usability of such quantitative photometric analysis is that at least for a longer period of time the optical measurement magnitude is a predetermined and clear function of the concentration of the material or substance. Consequently, the field of use of the photometric determination is rather limited and several chemical processes cannot rely upon such photometric techniques, such as, for instance, precipitation processes wherein the calibration curve is dependent upon the momentarily prevailing size of flakes or flocks (formation of flakes) and different optical parameters.